title: Predicting the thermodynamics by using state-dependent interactions.
abstract: We reconsider the structure-based route to coarse graining in which the coarse-grained model is defined in such a way to reproduce some distribution functions of the original system as accurately as possible. We consider standard expressions for pressure and chemical potential applied to this family of coarse-grained models with density-dependent interactions and show that they only provide approximations to the pressure and chemical potential of the underlying original system. These approximations are then carefully compared in two cases: we consider a generic microscopic system in the low-density regime and polymer solutions under good-solvent conditions. Moreover, we show that the state-dependent potentials depend on the ensemble in which they have been derived. Therefore, care must be used in applying canonical state-dependent potentials to predict phase lines, which is typically performed in other ensembles.
authors.affiliation: Dipartimento di Scienze Fisiche e Chimiche, Università dell'Aquila, V. Vetoio 10, Loc. Coppito, I-67100 L'Aquila, Italy. giuseppe.dadamo@aquila.infn.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: D'Adamo
authors.forename: Andrea
authors.initials: A
authors.lastname: Pelissetto
authors.forename: Carlo
authors.initials: C
authors.lastname: Pierleoni
mesh_terms: D011108:Polymers / Q000737:chemistry*; D011312:Pressure; D012996:Solutions; D013816:Thermodynamics
chemical_list: D011108:Polymers; D012996:Solutions